1. Field of the Invention
The present invention generally relates to image data recording apparatuses and image data recording methods for recording movies and still images. More particularly, though not exclusively, the present invention relates to an image data recording apparatus and an image data recording method that use different write spaces on a data recording medium to record image data.
2. Description of the Related Art
Recently, digital cameras and digital video cameras that record movies and still images on recording media, such as flash memory cards, have been widely used. Some of these electronic apparatuses adopt the FAT (File Allocation Table) system to record data on a recording medium. The FAT system manages used spaces and unused spaces on a recording medium using a table. In response to a data write request, the electronic apparatuses determine the unused spaces in which new data is written according to the table, and write the data in the determined unused spaces.
However, in the FAT system, repetition of file write and file delete operations mixes up the used spaces and the unused spaces. As a result, a circumstance where successive free spaces undesirably decrease (i.e., fragmentation) occurs. The presence of the fragmentation decreases the speed of a write operation. Therefore, the fragmentation is undesirable to record movies requiring real-time processing. Thus, the digital cameras and digital video cameras mentioned above may have such fragmentation caused by repetition of the write and delete operations on the memory card.
An earlier application of Japanese Patent Laid-Open No. 2000-267904 suggested a solution to the above-described problem. In this solution, whether the data to be recorded requires the real-time processing or not is a parameter that is determined first. According to free-space information of a recording medium, movie data requiring real-time processing is recorded in blocks with a high transfer rate. On the other hand, according to the free-space information of the recording medium, still image data not requiring real-time processing is recorded in blocks with a low transfer rate.
Now, features of an invention described in the above-cited Japanese Patent Laid-Open No. 2000-267904 are described more specifically. First, the data recording apparatus finds out the numbers of used clusters and unused clusters on a block-by-block basis (see FIG. 7A and FIG. 7B). The data recording apparatus sorts the blocks in ascending order of the number of unused clusters, and manages the result as the free-space information of the recording medium. On the basis of this free-space information, the data recording apparatus uses different blocks depending on the types of data to be recorded, i.e., movie data or still image data (see FIG. 7C).
However, in the configuration according to the invention of Japanese Patent Laid-Open No. 2000-267904 described above, all the movie data is written in the blocks with a high transfer rate, therefore the blocks with a high transfer rate may be unnecessarily used. As a result, the recordable time for the blocks with a high transfer rate rapidly decreases.
In light of the aforementioned, it becomes difficult to record long movies or the like. In addition, since the price-per-bit of memory cards used by image data recording apparatuses is significantly expensive, the efficient utilization of memory cards is desired.